2 * Copyright (C) 1995 Linus Torvalds
3 * Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs.
4 * Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar
6 #include <linux/sched.h> /* test_thread_flag(), ... */
7 #include <linux/kdebug.h> /* oops_begin/end, ... */
8 #include <linux/module.h> /* search_exception_table */
9 #include <linux/bootmem.h> /* max_low_pfn */
10 #include <linux/kprobes.h> /* NOKPROBE_SYMBOL, ... */
11 #include <linux/mmiotrace.h> /* kmmio_handler, ... */
12 #include <linux/perf_event.h> /* perf_sw_event */
13 #include <linux/hugetlb.h> /* hstate_index_to_shift */
14 #include <linux/prefetch.h> /* prefetchw */
15 #include <linux/context_tracking.h> /* exception_enter(), ... */
16 #include <linux/uaccess.h> /* faulthandler_disabled() */
18 #include <asm/traps.h> /* dotraplinkage, ... */
19 #include <asm/pgalloc.h> /* pgd_*(), ... */
20 #include <asm/kmemcheck.h> /* kmemcheck_*(), ... */
21 #include <asm/fixmap.h> /* VSYSCALL_ADDR */
22 #include <asm/vsyscall.h> /* emulate_vsyscall */
24 #define CREATE_TRACE_POINTS
25 #include <asm/trace/exceptions.h>
28 * Page fault error code bits:
30 * bit 0 == 0: no page found 1: protection fault
31 * bit 1 == 0: read access 1: write access
32 * bit 2 == 0: kernel-mode access 1: user-mode access
33 * bit 3 == 1: use of reserved bit detected
34 * bit 4 == 1: fault was an instruction fetch
36 enum x86_pf_error_code
{
46 * Returns 0 if mmiotrace is disabled, or if the fault is not
47 * handled by mmiotrace:
49 static nokprobe_inline
int
50 kmmio_fault(struct pt_regs
*regs
, unsigned long addr
)
52 if (unlikely(is_kmmio_active()))
53 if (kmmio_handler(regs
, addr
) == 1)
58 static nokprobe_inline
int kprobes_fault(struct pt_regs
*regs
)
62 /* kprobe_running() needs smp_processor_id() */
63 if (kprobes_built_in() && !user_mode(regs
)) {
65 if (kprobe_running() && kprobe_fault_handler(regs
, 14))
78 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
79 * Check that here and ignore it.
83 * Sometimes the CPU reports invalid exceptions on prefetch.
84 * Check that here and ignore it.
86 * Opcode checker based on code by Richard Brunner.
89 check_prefetch_opcode(struct pt_regs
*regs
, unsigned char *instr
,
90 unsigned char opcode
, int *prefetch
)
92 unsigned char instr_hi
= opcode
& 0xf0;
93 unsigned char instr_lo
= opcode
& 0x0f;
99 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
100 * In X86_64 long mode, the CPU will signal invalid
101 * opcode if some of these prefixes are present so
102 * X86_64 will never get here anyway
104 return ((instr_lo
& 7) == 0x6);
108 * In AMD64 long mode 0x40..0x4F are valid REX prefixes
109 * Need to figure out under what instruction mode the
110 * instruction was issued. Could check the LDT for lm,
111 * but for now it's good enough to assume that long
112 * mode only uses well known segments or kernel.
114 return (!user_mode(regs
) || user_64bit_mode(regs
));
117 /* 0x64 thru 0x67 are valid prefixes in all modes. */
118 return (instr_lo
& 0xC) == 0x4;
120 /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
121 return !instr_lo
|| (instr_lo
>>1) == 1;
123 /* Prefetch instruction is 0x0F0D or 0x0F18 */
124 if (probe_kernel_address(instr
, opcode
))
127 *prefetch
= (instr_lo
== 0xF) &&
128 (opcode
== 0x0D || opcode
== 0x18);
136 is_prefetch(struct pt_regs
*regs
, unsigned long error_code
, unsigned long addr
)
138 unsigned char *max_instr
;
139 unsigned char *instr
;
143 * If it was a exec (instruction fetch) fault on NX page, then
144 * do not ignore the fault:
146 if (error_code
& PF_INSTR
)
149 instr
= (void *)convert_ip_to_linear(current
, regs
);
150 max_instr
= instr
+ 15;
152 if (user_mode(regs
) && instr
>= (unsigned char *)TASK_SIZE_MAX
)
155 while (instr
< max_instr
) {
156 unsigned char opcode
;
158 if (probe_kernel_address(instr
, opcode
))
163 if (!check_prefetch_opcode(regs
, instr
, opcode
, &prefetch
))
170 force_sig_info_fault(int si_signo
, int si_code
, unsigned long address
,
171 struct task_struct
*tsk
, int fault
)
176 info
.si_signo
= si_signo
;
178 info
.si_code
= si_code
;
179 info
.si_addr
= (void __user
*)address
;
180 if (fault
& VM_FAULT_HWPOISON_LARGE
)
181 lsb
= hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault
));
182 if (fault
& VM_FAULT_HWPOISON
)
184 info
.si_addr_lsb
= lsb
;
186 force_sig_info(si_signo
, &info
, tsk
);
189 DEFINE_SPINLOCK(pgd_lock
);
193 static inline pmd_t
*vmalloc_sync_one(pgd_t
*pgd
, unsigned long address
)
195 unsigned index
= pgd_index(address
);
201 pgd_k
= init_mm
.pgd
+ index
;
203 if (!pgd_present(*pgd_k
))
207 * set_pgd(pgd, *pgd_k); here would be useless on PAE
208 * and redundant with the set_pmd() on non-PAE. As would
211 pud
= pud_offset(pgd
, address
);
212 pud_k
= pud_offset(pgd_k
, address
);
213 if (!pud_present(*pud_k
))
216 pmd
= pmd_offset(pud
, address
);
217 pmd_k
= pmd_offset(pud_k
, address
);
218 if (!pmd_present(*pmd_k
))
221 if (!pmd_present(*pmd
))
222 set_pmd(pmd
, *pmd_k
);
224 BUG_ON(pmd_page(*pmd
) != pmd_page(*pmd_k
));
229 void vmalloc_sync_all(void)
231 unsigned long address
;
233 if (SHARED_KERNEL_PMD
)
236 for (address
= VMALLOC_START
& PMD_MASK
;
237 address
>= TASK_SIZE
&& address
< FIXADDR_TOP
;
238 address
+= PMD_SIZE
) {
241 spin_lock(&pgd_lock
);
242 list_for_each_entry(page
, &pgd_list
, lru
) {
243 spinlock_t
*pgt_lock
;
246 /* the pgt_lock only for Xen */
247 pgt_lock
= &pgd_page_get_mm(page
)->page_table_lock
;
250 ret
= vmalloc_sync_one(page_address(page
), address
);
251 spin_unlock(pgt_lock
);
256 spin_unlock(&pgd_lock
);
263 * Handle a fault on the vmalloc or module mapping area
265 static noinline
int vmalloc_fault(unsigned long address
)
267 unsigned long pgd_paddr
;
271 /* Make sure we are in vmalloc area: */
272 if (!(address
>= VMALLOC_START
&& address
< VMALLOC_END
))
275 WARN_ON_ONCE(in_nmi());
278 * Synchronize this task's top level page-table
279 * with the 'reference' page table.
281 * Do _not_ use "current" here. We might be inside
282 * an interrupt in the middle of a task switch..
284 pgd_paddr
= read_cr3();
285 pmd_k
= vmalloc_sync_one(__va(pgd_paddr
), address
);
289 pte_k
= pte_offset_kernel(pmd_k
, address
);
290 if (!pte_present(*pte_k
))
295 NOKPROBE_SYMBOL(vmalloc_fault
);
298 * Did it hit the DOS screen memory VA from vm86 mode?
301 check_v8086_mode(struct pt_regs
*regs
, unsigned long address
,
302 struct task_struct
*tsk
)
307 if (!v8086_mode(regs
) || !tsk
->thread
.vm86
)
310 bit
= (address
- 0xA0000) >> PAGE_SHIFT
;
312 tsk
->thread
.vm86
->screen_bitmap
|= 1 << bit
;
316 static bool low_pfn(unsigned long pfn
)
318 return pfn
< max_low_pfn
;
321 static void dump_pagetable(unsigned long address
)
323 pgd_t
*base
= __va(read_cr3());
324 pgd_t
*pgd
= &base
[pgd_index(address
)];
328 #ifdef CONFIG_X86_PAE
329 printk("*pdpt = %016Lx ", pgd_val(*pgd
));
330 if (!low_pfn(pgd_val(*pgd
) >> PAGE_SHIFT
) || !pgd_present(*pgd
))
333 pmd
= pmd_offset(pud_offset(pgd
, address
), address
);
334 printk(KERN_CONT
"*pde = %0*Lx ", sizeof(*pmd
) * 2, (u64
)pmd_val(*pmd
));
337 * We must not directly access the pte in the highpte
338 * case if the page table is located in highmem.
339 * And let's rather not kmap-atomic the pte, just in case
340 * it's allocated already:
342 if (!low_pfn(pmd_pfn(*pmd
)) || !pmd_present(*pmd
) || pmd_large(*pmd
))
345 pte
= pte_offset_kernel(pmd
, address
);
346 printk("*pte = %0*Lx ", sizeof(*pte
) * 2, (u64
)pte_val(*pte
));
351 #else /* CONFIG_X86_64: */
353 void vmalloc_sync_all(void)
355 sync_global_pgds(VMALLOC_START
& PGDIR_MASK
, VMALLOC_END
, 0);
361 * Handle a fault on the vmalloc area
363 * This assumes no large pages in there.
365 static noinline
int vmalloc_fault(unsigned long address
)
367 pgd_t
*pgd
, *pgd_ref
;
368 pud_t
*pud
, *pud_ref
;
369 pmd_t
*pmd
, *pmd_ref
;
370 pte_t
*pte
, *pte_ref
;
372 /* Make sure we are in vmalloc area: */
373 if (!(address
>= VMALLOC_START
&& address
< VMALLOC_END
))
376 WARN_ON_ONCE(in_nmi());
379 * Copy kernel mappings over when needed. This can also
380 * happen within a race in page table update. In the later
383 pgd
= pgd_offset(current
->active_mm
, address
);
384 pgd_ref
= pgd_offset_k(address
);
385 if (pgd_none(*pgd_ref
))
388 if (pgd_none(*pgd
)) {
389 set_pgd(pgd
, *pgd_ref
);
390 arch_flush_lazy_mmu_mode();
392 BUG_ON(pgd_page_vaddr(*pgd
) != pgd_page_vaddr(*pgd_ref
));
396 * Below here mismatches are bugs because these lower tables
400 pud
= pud_offset(pgd
, address
);
401 pud_ref
= pud_offset(pgd_ref
, address
);
402 if (pud_none(*pud_ref
))
405 if (pud_none(*pud
) || pud_page_vaddr(*pud
) != pud_page_vaddr(*pud_ref
))
408 pmd
= pmd_offset(pud
, address
);
409 pmd_ref
= pmd_offset(pud_ref
, address
);
410 if (pmd_none(*pmd_ref
))
413 if (pmd_none(*pmd
) || pmd_page(*pmd
) != pmd_page(*pmd_ref
))
416 pte_ref
= pte_offset_kernel(pmd_ref
, address
);
417 if (!pte_present(*pte_ref
))
420 pte
= pte_offset_kernel(pmd
, address
);
423 * Don't use pte_page here, because the mappings can point
424 * outside mem_map, and the NUMA hash lookup cannot handle
427 if (!pte_present(*pte
) || pte_pfn(*pte
) != pte_pfn(*pte_ref
))
432 NOKPROBE_SYMBOL(vmalloc_fault
);
434 #ifdef CONFIG_CPU_SUP_AMD
435 static const char errata93_warning
[] =
437 "******* Your BIOS seems to not contain a fix for K8 errata #93\n"
438 "******* Working around it, but it may cause SEGVs or burn power.\n"
439 "******* Please consider a BIOS update.\n"
440 "******* Disabling USB legacy in the BIOS may also help.\n";
444 * No vm86 mode in 64-bit mode:
447 check_v8086_mode(struct pt_regs
*regs
, unsigned long address
,
448 struct task_struct
*tsk
)
452 static int bad_address(void *p
)
456 return probe_kernel_address((unsigned long *)p
, dummy
);
459 static void dump_pagetable(unsigned long address
)
461 pgd_t
*base
= __va(read_cr3() & PHYSICAL_PAGE_MASK
);
462 pgd_t
*pgd
= base
+ pgd_index(address
);
467 if (bad_address(pgd
))
470 printk("PGD %lx ", pgd_val(*pgd
));
472 if (!pgd_present(*pgd
))
475 pud
= pud_offset(pgd
, address
);
476 if (bad_address(pud
))
479 printk("PUD %lx ", pud_val(*pud
));
480 if (!pud_present(*pud
) || pud_large(*pud
))
483 pmd
= pmd_offset(pud
, address
);
484 if (bad_address(pmd
))
487 printk("PMD %lx ", pmd_val(*pmd
));
488 if (!pmd_present(*pmd
) || pmd_large(*pmd
))
491 pte
= pte_offset_kernel(pmd
, address
);
492 if (bad_address(pte
))
495 printk("PTE %lx", pte_val(*pte
));
503 #endif /* CONFIG_X86_64 */
506 * Workaround for K8 erratum #93 & buggy BIOS.
508 * BIOS SMM functions are required to use a specific workaround
509 * to avoid corruption of the 64bit RIP register on C stepping K8.
511 * A lot of BIOS that didn't get tested properly miss this.
513 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
514 * Try to work around it here.
516 * Note we only handle faults in kernel here.
517 * Does nothing on 32-bit.
519 static int is_errata93(struct pt_regs
*regs
, unsigned long address
)
521 #if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
522 if (boot_cpu_data
.x86_vendor
!= X86_VENDOR_AMD
523 || boot_cpu_data
.x86
!= 0xf)
526 if (address
!= regs
->ip
)
529 if ((address
>> 32) != 0)
532 address
|= 0xffffffffUL
<< 32;
533 if ((address
>= (u64
)_stext
&& address
<= (u64
)_etext
) ||
534 (address
>= MODULES_VADDR
&& address
<= MODULES_END
)) {
535 printk_once(errata93_warning
);
544 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
545 * to illegal addresses >4GB.
547 * We catch this in the page fault handler because these addresses
548 * are not reachable. Just detect this case and return. Any code
549 * segment in LDT is compatibility mode.
551 static int is_errata100(struct pt_regs
*regs
, unsigned long address
)
554 if ((regs
->cs
== __USER32_CS
|| (regs
->cs
& (1<<2))) && (address
>> 32))
560 static int is_f00f_bug(struct pt_regs
*regs
, unsigned long address
)
562 #ifdef CONFIG_X86_F00F_BUG
566 * Pentium F0 0F C7 C8 bug workaround:
568 if (boot_cpu_has_bug(X86_BUG_F00F
)) {
569 nr
= (address
- idt_descr
.address
) >> 3;
572 do_invalid_op(regs
, 0);
580 static const char nx_warning
[] = KERN_CRIT
581 "kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n";
582 static const char smep_warning
[] = KERN_CRIT
583 "unable to execute userspace code (SMEP?) (uid: %d)\n";
586 show_fault_oops(struct pt_regs
*regs
, unsigned long error_code
,
587 unsigned long address
)
589 if (!oops_may_print())
592 if (error_code
& PF_INSTR
) {
597 pgd
= __va(read_cr3() & PHYSICAL_PAGE_MASK
);
598 pgd
+= pgd_index(address
);
600 pte
= lookup_address_in_pgd(pgd
, address
, &level
);
602 if (pte
&& pte_present(*pte
) && !pte_exec(*pte
))
603 printk(nx_warning
, from_kuid(&init_user_ns
, current_uid()));
604 if (pte
&& pte_present(*pte
) && pte_exec(*pte
) &&
605 (pgd_flags(*pgd
) & _PAGE_USER
) &&
606 (__read_cr4() & X86_CR4_SMEP
))
607 printk(smep_warning
, from_kuid(&init_user_ns
, current_uid()));
610 printk(KERN_ALERT
"BUG: unable to handle kernel ");
611 if (address
< PAGE_SIZE
)
612 printk(KERN_CONT
"NULL pointer dereference");
614 printk(KERN_CONT
"paging request");
616 printk(KERN_CONT
" at %p\n", (void *) address
);
617 printk(KERN_ALERT
"IP:");
618 printk_address(regs
->ip
);
620 dump_pagetable(address
);
624 pgtable_bad(struct pt_regs
*regs
, unsigned long error_code
,
625 unsigned long address
)
627 struct task_struct
*tsk
;
631 flags
= oops_begin();
635 printk(KERN_ALERT
"%s: Corrupted page table at address %lx\n",
637 dump_pagetable(address
);
639 tsk
->thread
.cr2
= address
;
640 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
641 tsk
->thread
.error_code
= error_code
;
643 if (__die("Bad pagetable", regs
, error_code
))
646 oops_end(flags
, regs
, sig
);
650 no_context(struct pt_regs
*regs
, unsigned long error_code
,
651 unsigned long address
, int signal
, int si_code
)
653 struct task_struct
*tsk
= current
;
657 /* Are we prepared to handle this kernel fault? */
658 if (fixup_exception(regs
)) {
660 * Any interrupt that takes a fault gets the fixup. This makes
661 * the below recursive fault logic only apply to a faults from
668 * Per the above we're !in_interrupt(), aka. task context.
670 * In this case we need to make sure we're not recursively
671 * faulting through the emulate_vsyscall() logic.
673 if (current_thread_info()->sig_on_uaccess_error
&& signal
) {
674 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
675 tsk
->thread
.error_code
= error_code
| PF_USER
;
676 tsk
->thread
.cr2
= address
;
678 /* XXX: hwpoison faults will set the wrong code. */
679 force_sig_info_fault(signal
, si_code
, address
, tsk
, 0);
683 * Barring that, we can do the fixup and be happy.
691 * Valid to do another page fault here, because if this fault
692 * had been triggered by is_prefetch fixup_exception would have
697 * Hall of shame of CPU/BIOS bugs.
699 if (is_prefetch(regs
, error_code
, address
))
702 if (is_errata93(regs
, address
))
706 * Oops. The kernel tried to access some bad page. We'll have to
707 * terminate things with extreme prejudice:
709 flags
= oops_begin();
711 show_fault_oops(regs
, error_code
, address
);
713 if (task_stack_end_corrupted(tsk
))
714 printk(KERN_EMERG
"Thread overran stack, or stack corrupted\n");
716 tsk
->thread
.cr2
= address
;
717 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
718 tsk
->thread
.error_code
= error_code
;
721 if (__die("Oops", regs
, error_code
))
724 /* Executive summary in case the body of the oops scrolled away */
725 printk(KERN_DEFAULT
"CR2: %016lx\n", address
);
727 oops_end(flags
, regs
, sig
);
731 * Print out info about fatal segfaults, if the show_unhandled_signals
735 show_signal_msg(struct pt_regs
*regs
, unsigned long error_code
,
736 unsigned long address
, struct task_struct
*tsk
)
738 if (!unhandled_signal(tsk
, SIGSEGV
))
741 if (!printk_ratelimit())
744 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
745 task_pid_nr(tsk
) > 1 ? KERN_INFO
: KERN_EMERG
,
746 tsk
->comm
, task_pid_nr(tsk
), address
,
747 (void *)regs
->ip
, (void *)regs
->sp
, error_code
);
749 print_vma_addr(KERN_CONT
" in ", regs
->ip
);
751 printk(KERN_CONT
"\n");
755 __bad_area_nosemaphore(struct pt_regs
*regs
, unsigned long error_code
,
756 unsigned long address
, int si_code
)
758 struct task_struct
*tsk
= current
;
760 /* User mode accesses just cause a SIGSEGV */
761 if (error_code
& PF_USER
) {
763 * It's possible to have interrupts off here:
768 * Valid to do another page fault here because this one came
771 if (is_prefetch(regs
, error_code
, address
))
774 if (is_errata100(regs
, address
))
779 * Instruction fetch faults in the vsyscall page might need
782 if (unlikely((error_code
& PF_INSTR
) &&
783 ((address
& ~0xfff) == VSYSCALL_ADDR
))) {
784 if (emulate_vsyscall(regs
, address
))
788 /* Kernel addresses are always protection faults: */
789 if (address
>= TASK_SIZE
)
790 error_code
|= PF_PROT
;
792 if (likely(show_unhandled_signals
))
793 show_signal_msg(regs
, error_code
, address
, tsk
);
795 tsk
->thread
.cr2
= address
;
796 tsk
->thread
.error_code
= error_code
;
797 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
799 force_sig_info_fault(SIGSEGV
, si_code
, address
, tsk
, 0);
804 if (is_f00f_bug(regs
, address
))
807 no_context(regs
, error_code
, address
, SIGSEGV
, si_code
);
811 bad_area_nosemaphore(struct pt_regs
*regs
, unsigned long error_code
,
812 unsigned long address
)
814 __bad_area_nosemaphore(regs
, error_code
, address
, SEGV_MAPERR
);
818 __bad_area(struct pt_regs
*regs
, unsigned long error_code
,
819 unsigned long address
, int si_code
)
821 struct mm_struct
*mm
= current
->mm
;
824 * Something tried to access memory that isn't in our memory map..
825 * Fix it, but check if it's kernel or user first..
827 up_read(&mm
->mmap_sem
);
829 __bad_area_nosemaphore(regs
, error_code
, address
, si_code
);
833 bad_area(struct pt_regs
*regs
, unsigned long error_code
, unsigned long address
)
835 __bad_area(regs
, error_code
, address
, SEGV_MAPERR
);
839 bad_area_access_error(struct pt_regs
*regs
, unsigned long error_code
,
840 unsigned long address
)
842 __bad_area(regs
, error_code
, address
, SEGV_ACCERR
);
846 do_sigbus(struct pt_regs
*regs
, unsigned long error_code
, unsigned long address
,
849 struct task_struct
*tsk
= current
;
850 int code
= BUS_ADRERR
;
852 /* Kernel mode? Handle exceptions or die: */
853 if (!(error_code
& PF_USER
)) {
854 no_context(regs
, error_code
, address
, SIGBUS
, BUS_ADRERR
);
858 /* User-space => ok to do another page fault: */
859 if (is_prefetch(regs
, error_code
, address
))
862 tsk
->thread
.cr2
= address
;
863 tsk
->thread
.error_code
= error_code
;
864 tsk
->thread
.trap_nr
= X86_TRAP_PF
;
866 #ifdef CONFIG_MEMORY_FAILURE
867 if (fault
& (VM_FAULT_HWPOISON
|VM_FAULT_HWPOISON_LARGE
)) {
869 "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
870 tsk
->comm
, tsk
->pid
, address
);
871 code
= BUS_MCEERR_AR
;
874 force_sig_info_fault(SIGBUS
, code
, address
, tsk
, fault
);
878 mm_fault_error(struct pt_regs
*regs
, unsigned long error_code
,
879 unsigned long address
, unsigned int fault
)
881 if (fatal_signal_pending(current
) && !(error_code
& PF_USER
)) {
882 no_context(regs
, error_code
, address
, 0, 0);
886 if (fault
& VM_FAULT_OOM
) {
887 /* Kernel mode? Handle exceptions or die: */
888 if (!(error_code
& PF_USER
)) {
889 no_context(regs
, error_code
, address
,
890 SIGSEGV
, SEGV_MAPERR
);
895 * We ran out of memory, call the OOM killer, and return the
896 * userspace (which will retry the fault, or kill us if we got
899 pagefault_out_of_memory();
901 if (fault
& (VM_FAULT_SIGBUS
|VM_FAULT_HWPOISON
|
902 VM_FAULT_HWPOISON_LARGE
))
903 do_sigbus(regs
, error_code
, address
, fault
);
904 else if (fault
& VM_FAULT_SIGSEGV
)
905 bad_area_nosemaphore(regs
, error_code
, address
);
911 static int spurious_fault_check(unsigned long error_code
, pte_t
*pte
)
913 if ((error_code
& PF_WRITE
) && !pte_write(*pte
))
916 if ((error_code
& PF_INSTR
) && !pte_exec(*pte
))
923 * Handle a spurious fault caused by a stale TLB entry.
925 * This allows us to lazily refresh the TLB when increasing the
926 * permissions of a kernel page (RO -> RW or NX -> X). Doing it
927 * eagerly is very expensive since that implies doing a full
928 * cross-processor TLB flush, even if no stale TLB entries exist
929 * on other processors.
931 * Spurious faults may only occur if the TLB contains an entry with
932 * fewer permission than the page table entry. Non-present (P = 0)
933 * and reserved bit (R = 1) faults are never spurious.
935 * There are no security implications to leaving a stale TLB when
936 * increasing the permissions on a page.
938 * Returns non-zero if a spurious fault was handled, zero otherwise.
940 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3
941 * (Optional Invalidation).
944 spurious_fault(unsigned long error_code
, unsigned long address
)
953 * Only writes to RO or instruction fetches from NX may cause
956 * These could be from user or supervisor accesses but the TLB
957 * is only lazily flushed after a kernel mapping protection
958 * change, so user accesses are not expected to cause spurious
961 if (error_code
!= (PF_WRITE
| PF_PROT
)
962 && error_code
!= (PF_INSTR
| PF_PROT
))
965 pgd
= init_mm
.pgd
+ pgd_index(address
);
966 if (!pgd_present(*pgd
))
969 pud
= pud_offset(pgd
, address
);
970 if (!pud_present(*pud
))
974 return spurious_fault_check(error_code
, (pte_t
*) pud
);
976 pmd
= pmd_offset(pud
, address
);
977 if (!pmd_present(*pmd
))
981 return spurious_fault_check(error_code
, (pte_t
*) pmd
);
983 pte
= pte_offset_kernel(pmd
, address
);
984 if (!pte_present(*pte
))
987 ret
= spurious_fault_check(error_code
, pte
);
992 * Make sure we have permissions in PMD.
993 * If not, then there's a bug in the page tables:
995 ret
= spurious_fault_check(error_code
, (pte_t
*) pmd
);
996 WARN_ONCE(!ret
, "PMD has incorrect permission bits\n");
1000 NOKPROBE_SYMBOL(spurious_fault
);
1002 int show_unhandled_signals
= 1;
1005 access_error(unsigned long error_code
, struct vm_area_struct
*vma
)
1007 if (error_code
& PF_WRITE
) {
1008 /* write, present and write, not present: */
1009 if (unlikely(!(vma
->vm_flags
& VM_WRITE
)))
1014 /* read, present: */
1015 if (unlikely(error_code
& PF_PROT
))
1018 /* read, not present: */
1019 if (unlikely(!(vma
->vm_flags
& (VM_READ
| VM_EXEC
| VM_WRITE
))))
1025 static int fault_in_kernel_space(unsigned long address
)
1027 return address
>= TASK_SIZE_MAX
;
1030 static inline bool smap_violation(int error_code
, struct pt_regs
*regs
)
1032 if (!IS_ENABLED(CONFIG_X86_SMAP
))
1035 if (!static_cpu_has(X86_FEATURE_SMAP
))
1038 if (error_code
& PF_USER
)
1041 if (!user_mode(regs
) && (regs
->flags
& X86_EFLAGS_AC
))
1048 * This routine handles page faults. It determines the address,
1049 * and the problem, and then passes it off to one of the appropriate
1052 * This function must have noinline because both callers
1053 * {,trace_}do_page_fault() have notrace on. Having this an actual function
1054 * guarantees there's a function trace entry.
1056 static noinline
void
1057 __do_page_fault(struct pt_regs
*regs
, unsigned long error_code
,
1058 unsigned long address
)
1060 struct vm_area_struct
*vma
;
1061 struct task_struct
*tsk
;
1062 struct mm_struct
*mm
;
1063 int fault
, major
= 0;
1064 unsigned int flags
= FAULT_FLAG_ALLOW_RETRY
| FAULT_FLAG_KILLABLE
;
1070 * Detect and handle instructions that would cause a page fault for
1071 * both a tracked kernel page and a userspace page.
1073 if (kmemcheck_active(regs
))
1074 kmemcheck_hide(regs
);
1075 prefetchw(&mm
->mmap_sem
);
1077 if (unlikely(kmmio_fault(regs
, address
)))
1081 * We fault-in kernel-space virtual memory on-demand. The
1082 * 'reference' page table is init_mm.pgd.
1084 * NOTE! We MUST NOT take any locks for this case. We may
1085 * be in an interrupt or a critical region, and should
1086 * only copy the information from the master page table,
1089 * This verifies that the fault happens in kernel space
1090 * (error_code & 4) == 0, and that the fault was not a
1091 * protection error (error_code & 9) == 0.
1093 if (unlikely(fault_in_kernel_space(address
))) {
1094 if (!(error_code
& (PF_RSVD
| PF_USER
| PF_PROT
))) {
1095 if (vmalloc_fault(address
) >= 0)
1098 if (kmemcheck_fault(regs
, address
, error_code
))
1102 /* Can handle a stale RO->RW TLB: */
1103 if (spurious_fault(error_code
, address
))
1106 /* kprobes don't want to hook the spurious faults: */
1107 if (kprobes_fault(regs
))
1110 * Don't take the mm semaphore here. If we fixup a prefetch
1111 * fault we could otherwise deadlock:
1113 bad_area_nosemaphore(regs
, error_code
, address
);
1118 /* kprobes don't want to hook the spurious faults: */
1119 if (unlikely(kprobes_fault(regs
)))
1122 if (unlikely(error_code
& PF_RSVD
))
1123 pgtable_bad(regs
, error_code
, address
);
1125 if (unlikely(smap_violation(error_code
, regs
))) {
1126 bad_area_nosemaphore(regs
, error_code
, address
);
1131 * If we're in an interrupt, have no user context or are running
1132 * in a region with pagefaults disabled then we must not take the fault
1134 if (unlikely(faulthandler_disabled() || !mm
)) {
1135 bad_area_nosemaphore(regs
, error_code
, address
);
1140 * It's safe to allow irq's after cr2 has been saved and the
1141 * vmalloc fault has been handled.
1143 * User-mode registers count as a user access even for any
1144 * potential system fault or CPU buglet:
1146 if (user_mode(regs
)) {
1148 error_code
|= PF_USER
;
1149 flags
|= FAULT_FLAG_USER
;
1151 if (regs
->flags
& X86_EFLAGS_IF
)
1155 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS
, 1, regs
, address
);
1157 if (error_code
& PF_WRITE
)
1158 flags
|= FAULT_FLAG_WRITE
;
1161 * When running in the kernel we expect faults to occur only to
1162 * addresses in user space. All other faults represent errors in
1163 * the kernel and should generate an OOPS. Unfortunately, in the
1164 * case of an erroneous fault occurring in a code path which already
1165 * holds mmap_sem we will deadlock attempting to validate the fault
1166 * against the address space. Luckily the kernel only validly
1167 * references user space from well defined areas of code, which are
1168 * listed in the exceptions table.
1170 * As the vast majority of faults will be valid we will only perform
1171 * the source reference check when there is a possibility of a
1172 * deadlock. Attempt to lock the address space, if we cannot we then
1173 * validate the source. If this is invalid we can skip the address
1174 * space check, thus avoiding the deadlock:
1176 if (unlikely(!down_read_trylock(&mm
->mmap_sem
))) {
1177 if ((error_code
& PF_USER
) == 0 &&
1178 !search_exception_tables(regs
->ip
)) {
1179 bad_area_nosemaphore(regs
, error_code
, address
);
1183 down_read(&mm
->mmap_sem
);
1186 * The above down_read_trylock() might have succeeded in
1187 * which case we'll have missed the might_sleep() from
1193 vma
= find_vma(mm
, address
);
1194 if (unlikely(!vma
)) {
1195 bad_area(regs
, error_code
, address
);
1198 if (likely(vma
->vm_start
<= address
))
1200 if (unlikely(!(vma
->vm_flags
& VM_GROWSDOWN
))) {
1201 bad_area(regs
, error_code
, address
);
1204 if (error_code
& PF_USER
) {
1206 * Accessing the stack below %sp is always a bug.
1207 * The large cushion allows instructions like enter
1208 * and pusha to work. ("enter $65535, $31" pushes
1209 * 32 pointers and then decrements %sp by 65535.)
1211 if (unlikely(address
+ 65536 + 32 * sizeof(unsigned long) < regs
->sp
)) {
1212 bad_area(regs
, error_code
, address
);
1216 if (unlikely(expand_stack(vma
, address
))) {
1217 bad_area(regs
, error_code
, address
);
1222 * Ok, we have a good vm_area for this memory access, so
1223 * we can handle it..
1226 if (unlikely(access_error(error_code
, vma
))) {
1227 bad_area_access_error(regs
, error_code
, address
);
1232 * If for any reason at all we couldn't handle the fault,
1233 * make sure we exit gracefully rather than endlessly redo
1234 * the fault. Since we never set FAULT_FLAG_RETRY_NOWAIT, if
1235 * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked.
1237 fault
= handle_mm_fault(mm
, vma
, address
, flags
);
1238 major
|= fault
& VM_FAULT_MAJOR
;
1241 * If we need to retry the mmap_sem has already been released,
1242 * and if there is a fatal signal pending there is no guarantee
1243 * that we made any progress. Handle this case first.
1245 if (unlikely(fault
& VM_FAULT_RETRY
)) {
1246 /* Retry at most once */
1247 if (flags
& FAULT_FLAG_ALLOW_RETRY
) {
1248 flags
&= ~FAULT_FLAG_ALLOW_RETRY
;
1249 flags
|= FAULT_FLAG_TRIED
;
1250 if (!fatal_signal_pending(tsk
))
1254 /* User mode? Just return to handle the fatal exception */
1255 if (flags
& FAULT_FLAG_USER
)
1258 /* Not returning to user mode? Handle exceptions or die: */
1259 no_context(regs
, error_code
, address
, SIGBUS
, BUS_ADRERR
);
1263 up_read(&mm
->mmap_sem
);
1264 if (unlikely(fault
& VM_FAULT_ERROR
)) {
1265 mm_fault_error(regs
, error_code
, address
, fault
);
1270 * Major/minor page fault accounting. If any of the events
1271 * returned VM_FAULT_MAJOR, we account it as a major fault.
1275 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ
, 1, regs
, address
);
1278 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN
, 1, regs
, address
);
1281 check_v8086_mode(regs
, address
, tsk
);
1283 NOKPROBE_SYMBOL(__do_page_fault
);
1285 dotraplinkage
void notrace
1286 do_page_fault(struct pt_regs
*regs
, unsigned long error_code
)
1288 unsigned long address
= read_cr2(); /* Get the faulting address */
1289 enum ctx_state prev_state
;
1292 * We must have this function tagged with __kprobes, notrace and call
1293 * read_cr2() before calling anything else. To avoid calling any kind
1294 * of tracing machinery before we've observed the CR2 value.
1296 * exception_{enter,exit}() contain all sorts of tracepoints.
1299 prev_state
= exception_enter();
1300 __do_page_fault(regs
, error_code
, address
);
1301 exception_exit(prev_state
);
1303 NOKPROBE_SYMBOL(do_page_fault
);
1305 #ifdef CONFIG_TRACING
1306 static nokprobe_inline
void
1307 trace_page_fault_entries(unsigned long address
, struct pt_regs
*regs
,
1308 unsigned long error_code
)
1310 if (user_mode(regs
))
1311 trace_page_fault_user(address
, regs
, error_code
);
1313 trace_page_fault_kernel(address
, regs
, error_code
);
1316 dotraplinkage
void notrace
1317 trace_do_page_fault(struct pt_regs
*regs
, unsigned long error_code
)
1320 * The exception_enter and tracepoint processing could
1321 * trigger another page faults (user space callchain
1322 * reading) and destroy the original cr2 value, so read
1323 * the faulting address now.
1325 unsigned long address
= read_cr2();
1326 enum ctx_state prev_state
;
1328 prev_state
= exception_enter();
1329 trace_page_fault_entries(address
, regs
, error_code
);
1330 __do_page_fault(regs
, error_code
, address
);
1331 exception_exit(prev_state
);
1333 NOKPROBE_SYMBOL(trace_do_page_fault
);
1334 #endif /* CONFIG_TRACING */